Re: Diffusion coefficients
> I wonder if there is any way we could make use of an electric field
> in an aquarium like maybe to pull nutrients around with? Maybe it
> would make the plants grow better!
As luck would have it, I have done just such an experiment. I would
NOT recommend that anyone try to duplicate these results at home.
Even though I am a trained professional, there were some well known
unfortunate consequences of the experiment when it was first performed
40 months ago.
Electro-Stimulation With Substrate Heating Coils
I have been doing some experiments with substrate heating and have
come across some rather strange but apparently very useful results.
First, some background. We have an old 29 gallon tank that used to be
a quarantine/hospital tank. We haven't bought any new fish lately and
we don't really believe in treating sick fish with all the patent
medicines available, so the tank hasn't used for awhile. I decided
to set it up as a heating coil experiment and try some of the ideas
Dan Resler and Uwe Behle have discussed.
Other background: one night Karla was telling me about one of her
biochemistry procedures called "sodium dodecyl sulphate Polyacrylamide
Gel Electrophoresis" (yes, she actually talks like that) called
SDS-PAGE for short. As best as I could interpret :-), electrophoresis
is used to determine relative molecular weights of enzymes and
proteins by putting them on a plate covered with gel and applying an
electric field. After a time, compounds with different molecular
weights will have migrated different distances across the plate and
you can tell what they may be. Or something like that. Anyway, that
conversation planted the seed of "electric fields and organic things"
in my head somewhere.
More background: a year or so ago, one of the net contributors, Jim
Hurley, was posting about a device he heard about that supposedly
uses electric fields or currents to denitrify water. He did some
experiments with it but had other problems that interfered with the
results, so I don't know what became of it. But, just the same,
another part of an interesting puzzle.
Before I go further, I would like to state that what I am describing
could have the potential for danger. Keep in mind that water and
electricity are a deadly combination and should not be trifled with.
I am a qualified electrical engineer and have taken appropriate
precautions with the setup I'm going to describe. I would strongly
dissuade any one from trying to dulpacate this until more information
is discovered about the processes involved.
Now that we've had the obligatory safety warning, let me get on with
this. The stated purpose of substrate heating coils is to create slow
convection currents that bring nutrients such as NH4++, Fe++, Ca++,
Mg++, etc. into the root zone for eventual adsorption by the plant
roots. Besides the water currents that keep the substrate rich with
nutrients, the coils add heat to increase plant metabolism. Finally,
the slow currents allow nitrifying bacteria in the substrate to reduce
oxygen levels so that the trace elements don't oxidize. So far, in my
experience, the coils have been shown to provide the plants with good
conditions for long term growth, but they have NOT been shown to
affect the growth rate. Always the greedy one, I am trying to find a
technique to increase the growth rate above the already rapid rate
allowed by CO2 injection. And I may have stumbled on to something.
I have tried to set up the 29 gallon tank in such a way that I can get
some fairly controlled results. I have divided the substrate into two
halves (right and left) by glueing a 4" tall piece of acrylic down the
middle. The barrier will divide the substrate into two halves but
will allow everything else in the tank to be shared. I am using
two old AquaClear 200s for mechanical filtration and two powerheads
centered in each half at the top of the back glass for water movement.
Two Tetra CO2 bells are next to each powerhead and fed by a Thomas
Narten CO2 generator. A 4' shoplight with a Triton and an UltraTriLux
bulb is centered over the tank, providing light from the top as well
as some from the ends. The substrate is 3" of 2-3mm quartz gravel
with Dupla laterite mixed in the bottom third. With the addition of
heating coils, the setup is very close to an "Optimum Aquarium".
I have been following our typical maintenance regimen: 25% water change
every two weeks, addition of 1 Duplaplant tablet at water changes, 2
Duplaplant-24 drops every day starting 3 days after a water change,
replace evaporation losses with tap water as needed. The water
hardness is maintained at 4.5 dKH and is 3 dGH. Enough CO2 is being
injected to hold the pH at just under 7.0, corresponding to about 15
The only significant difference is the way the heating coils are setup
in each half. The right half has 12' of 28 gauge insulated wire,
giving about 50 watts of heat with a 12v DC power supply. The left
half is the same, except I have used BARE WIRE instead of insulated
What I am trying to do is this: by creating an electric field in the
aquarium, I am trying to force the migration of cations (positively
charged ions like NH4+, Fe++, etc) down to the substrate and
negatively charged ions like (NO3-) to the top of the tank. The bare
wire has a linear drop from 12v to 0v along its length; it is laid in
a paired-serpentine pattern such that the two ends are together
giving an average 6v field at that point and the average at all
points along the length is 6v. The DC supply is connected as a -12v
supply, so the substrate will have a negative charge with respect to
I was using a "Solution Ground" (titanium probe) at the top of the
tank connected to a +6v supply to supply the other half of the field
giving a 12v potential from top to bottom. Since the water potential
is only 6v to ground, it should be perfectly safe to work in. When I
was planting plants, I could not detect or feel any electricity at
To enhance the effect of the electric field, I am overdosing the tank
with a chelated iron compound. This should greatly increase the
conductivity of the water. I am shooting for an iron level 100x as
much as is normal (10 ppm versus 0.1 ppm).
After watching the fish in the tank for awhile, I decided the probe
was not the best idea. The fishes lateral lines are very sensitive to
electric fields and they were apparently aligning themselves to the
field: they were all leaning toward the probe no matter what their
orientation. A very strange effect, indeed. To counter this, I ordered
some titanium wire from Edmund Scientific and ran a loop around the
top of the tank just below the water surface. This completely cured
the fishes tendency to lean.
The tank has been cycled and running for 6 weeks now. The tank has 6
medium sized M. Bosemani rainbows, 12 otocinclus, 4 corys and 2 small
farlowellas. The fish are fed 1/4 tsp of TetraBits daily.
The two halves of the tank are planted identically and symetrically.
Each half has:
6 stems of Rotala macrandra
12 stems of R. rotundifolia
3 stems Bacopa caroliniana
2 small Anubias barteri
1 Echinodorus bleheri
4 E. quadricostatus
4 Cryptocoryne wenditii
1 Samolus parviflorus
There were also 10 Malaysian trumpet snails (about 1/2" long) initially.
Their population seems to be steadily increasing.
The results so far are nothing short of amazing.
Plant growth is distinctly different on each side of the tank. On the
right side (insulated coils or "normal"), the growth is typical of our
other CO2 injected tanks: the stems plants need trimming about once
per week and the rosette plants put on two to three new leaves per
On the bare coil side or "special", the plant growth is more than I
hoped for. It is easily double what the right side has, both in
height as well as stem thickness and leaf size and density. I cannot
really justify this growth based on availability of more nutrients;
there must be some kind of electro-bio-stimulation going on. It's as
if the voltage potential in the water is supplementing the available
light energy to dramatically increase photosynthesis. There are far
more O2 bubbles on the left side plants than the right side.
If this were the only positive result, I would be more than happy.
However, as I observe the tank I have been noticing more and more
In a well lit tank, most green plants will have some reddish coloring
on the leaves nearest the light. The plants in the "normal" side exhibit
this. However, the plants in the "special" side have the exact
opposite effect: the leaves and stems near the bottom of the plant are
reddish and the top leaves are bright green! About the only reason I
can think of for this is the electric field: the Fe++ is being
prevented from getting to the top of the plant or perhaps even being
repelled by the negative charge at the top.
The Rotala macrandra, normally a plant with a mottled red-orange-green
appearance under good light, is exhibiting an even stranger
phenomenom. There are color gradations going from bottom to top: red
at the bottom, then orange, a tinge of blue and green at the top.
Much like the SDS-PAGE gel procedure, the electrical potential seems
to be holding various trace elements at various levels in the plants.
An obvious application of this is to grow plants specifically for
color coordinated landscape scenes: blue plants for blue gravel, etc.
I have also noted that the Malaysian snails do not seem to live on the
special side of the tank. I have never seen one over there and have
not noticed any in the gravel. I have noted, however, many empty
shells just over the acrylic barrier. It's as if they tried to scale
the wall and were zapped when the reached the other side. An electric
fence for snails, as it were.
Fish health has also been affected in a positive way. When we got the
otocinclus, they appeared to infected with ick. Since they were the
only ones around, we decided to buy them anyway. After being in the
tank for a day, we noticed fewer spots on them. Close observation
showed us that the ick was dropping off the fish and was actually
being attracted to the positively charged top wire. Unable to fulfill
its normal gravel-living growing phase, the infection was immediately
Water quality was also positively affected. We monitored the nitrogen
cycle from day one and noted that the cycle appeared to complete in
1/3 the normal 5 to 6 weeks and the levels of ammonia and nitrite
were very low (< 0.2 ppm each). We have also not been able to measure
ANY nitrate. We do note a constant low level bubbling at the positive
top wire and conjecture that the NO3- is being attracted to it and is
being electrolyzed into N2 and O2. This in itself is a significant
advancement in the aquarium State-of-the-Art.
The final noteworthy phenomenom is the affect on algae. Both sides of
the tank have had some minor "fuzz" algae. The otos have been keeping
it under control on the normal side. The special side seems to have
given plants the ability to repel the algae. If you look closely, you
can see small strands of algae growing in the plant leaves, but it is
standing straight up. Under careful observation, you can actually see
the algae begin to quiver, detach itself from the plant and head
straight for the top wire where it disappears in a little cloud of
I hesitate to report the final observation for fear of ridicule, but I
feel it is my duty to be as impartial as possible. I have not yet
confirmed the following, but an analysis is in progress. I will give
updates when the final assay is in.
We had some blue-green slime algae (cyanobacteria) developing in the
55 gallon tank. With all the positive benefits noted so, we decided
to move the affected plants to the special side of the 29 to see what
would happen. At first, nothing appeared to happen. We did notice
the slime algae beginning to loose it color right before the lights
went out and figured it was dying or dissolving.
The next day, it appeared that the slime algae had disappeared but on
closer examination noted a discoloration of the plant leaves where the
algae had been. They appeared to be a yellowish color. We removed
the plant from the tank and brushed the leaves where they were
discolored. The yellow color came off as a thin film with a metallic
sheen. As silly as this sounds, it appeared to be gold leaf. We took
a few of the samples down to the local assay office and are eagerly
awaiting the results. It looks like this hobby may finally pay off!